1. Field of the Invention
The present invention relates to a thin-film magnetic head for reading magnetic information on a hard disk or the like by utilizing a magnetoresistance effect, a head gimbal assembly, a hard disk apparatus, and a method of making a thin-film magnetic head.
2. Related Background Art
MR (Magneto Resistive) heads have been in use as thin-film magnetic heads for reading magnetic information on hard disks. The MR heads utilize a magnetoresistance effect in which a magnetic material changes its ohmic value due to changes in external magnetic fields (e.g., leakage magnetic fields from hard disks) when a current is caused to flow through the magnetic material. This magnetoresistance effect can be substantially realized by an MR film that stacks a pinned layer having a direction of magnetization that is fixed by exchange-coupling with an antiferromagnetic layer, a free layer having a direction of magnetization that varies according to external magnetic fields, an intermediate layer disposed therebetween. In GMR (Giant Magneto Resistive) heads utilizing a giant magnetoresistance effect, the intermediate layer is formed from an electrically conductive material such as Cu.
A predetermined sense current is supplied to the MR film of a magnetic head. Then, the angle between the respective directions of magnetization of the pinned layer and the free layer changes due to external magnetic fields. The resistance of the MR element is lowest when the respective directions of magnetization of the individual layers coincide with each other, and is highest when the directions of magnetization are opposite to each other. Reading such a change in resistance as a voltage value can reproduce the magnetic information written on hard disks.
Meanwhile, in thin-film magnetic heads, a CIP (Current In Plane) structure in which the sense current flows in the planar direction of the MR film and a CPP (Current Perpendicular to Plane) structure in which the sense current flows in a direction (film thickness direction) perpendicular to the MR film have been developed (for example, see Japanese Patent Application No. 2000-105912 (FIG. 2)). Since a magnetic shield layer itself can be used as an electrode, the later CPP structure is substantially free from short-circuiting (insulation failure) between the magnetic shield layer and MR film which may become problematic in the narrower lead gap to be achieved in the CIP structure. Therefore, the CPP structure is quite advantageous in attaining a higher recording density on hard disks. Examples of heads employing the CPP structure include TMR (Tunnel-type Magneto Resistive) heads utilizing the magneto resistance effect occurring in tunnel junctions, and CPP-GMR heads.